Hello, first of all excuse my English, it's not perfect.

Some time ago I read a one-shot about two siblings (twins: older sister and younger brother) who were in love with each other, and as the story unfolds we learn that they are the reincarnations of two lovers who commit suicide because they couldn't be together.

Also the older sister turns out to be a murderous maniac who would kill anyone who would interfere between her and her brother.

Both have black hair, the sister has long hair. That's all.

Anyone remembers the name? Thanks in advance.

The oneshot from Human System?

Yes, I found it, thank you.